In the catalytic hydroprocessing of hydrocarbon feedstocks particulate catalysts are used to promote such reactions as desulfurization, denitrogenation, demetallization, and cracking. This is done by contacting the particulate catalyst with hydrocarbon feedstocks such as gas oils, distillates (e.g., diesel and kerosene), naphthas and gasolines under conditions of elevated temperature and pressure and in the presence of hydrogen. With hydrodesulfurization, the organic sulfur components of the hydrocarbon feedstock are converted to hydrogen sulfide, and, with hydrodenitrogenation, the organic nitrogen components of the hydrocarbon feedstock are converted to ammonia.
A typical hydroprocessing catalyst contains one or more hydrogenation metal and, optionally, one or more promoter, that are supported on a porous refractory oxide support. The hydrogenation metal is typically a Group VIB metal or a Group VIII metal, or a combination of both such metals, that is used as an active component supported on a porous refractory oxide, such as, alumina. A promoter, such as phosphorous, may also be incorporated into the porous refractory oxide. These hydroprocessing catalysts are typically prepared by impregnation of the active components into the support by contacting it with an aqueous solution containing the active components in dissolved form. The impregnated support is then usually dried and calcined to convert the active metals and promoters to the oxide form. The catalyst is then activated, usually by sulfiding, to prepare it for use.
One method of preparing supported hydroprocessing catalysts is disclosed in U.S. Pat. No. 5,336,654. This patent teaches a method for the preparation of hydrotreating catalyst by impregnating an inorganic oxide material with a Group VIII metal salt of an acid and a Group VI heteropolyacid. The metals can be incorporated into the support by using one or more impregnations. After the impregnation of the support, the catalyst is dried to remove free water from the catalyst and then heat treated to a temperature of up to about 300° C. The impregnated support is then sulfided.
U.S. Pat. No. 5,338,717 discloses various methods of preparing a supported hydroprocessing catalyst. In one of the disclosed methods, several impregnation steps are used to prepare a catalyst. In this method, a support is first impregnated with a Group VI heteropolyacid followed by treating the impregnated support with an aqueous solution of a reducing agent. The impregnated treated support is further impregnated with a Group VIII metal salt of an acid followed by drying at a temperature of from about 20° C. to 200° C. and then sulfiding to form the final catalyst. In another of the disclosed methods, the support is first impregnated with both the Group VIII metal salt and the Group VI heteropolyacid, followed by drying at a temperature of from about 20° C. to 200° C. the impregnated dried support is then treated with a reducing agent, again dried, and sulfided to form the final catalyst.
Disclosed in U.S. Pat. No. 6,218,333 is a method of preparing a hydroprocessing catalyst by combining a porous support with an active metal so as to form a catalyst precursor having a volatile content. The volatiles are driven from the catalyst precursor under non-calcination temperature conditions while treating the catalyst precursor with a sulfur containing compound.